有时，滤清器外部看似清洁，但是其内部已经非常脏了，此时必须立即进行更换。

Sometimes, filters, but its exterior looks clean inside have very dirty, must immediately replaced.

youdao

有时，滤清器外部看似清洁，但是其内部已经非常脏了，此时必须立即进行更换。

Sometimes, filters, but its exterior looks clean inside have very dirty, must immediately replaced.

youdao